Building block



FIG. 1 is a top perspective view of a building block showing my new design;

FIG. 2 is a bottom perspective view of the building block of FIG. 1;

FIG. 3 is a top view of the building block of FIG. 1;

FIG. 4 is a bottom view of the building block of FIG. 1;

FIG. 5 is a left side elevation view of the building block of FIG. 1;

FIG. 6 is a right side elevation view of the building block of FIG. 1;

FIG. 7 is a rear elevation view of the building block of FIG. 1; and,

FIG. 8 is a front elevation view of the building block of FIG. 1. 

CLAIM The ornamental design for a building block, as shown and described. 